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78xcgxl

AU Engine in XC falcon cuts in and out when reved past 2500 rpm

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Hi all,

 

I have been facing this problem with the AU engine in my XC falcon. At first and before having a working tacho i though i was simply hitting the rev limiter but as soon as i got the tacho working and letting my mate take the car for a test drive the problem was discovered. When driving the car it will not rev past 2500 rpm and will start cutting in and out, shaking and surges. The car drives great up and until that point. However when the car is stationary in neutral it will happily rev past 2500 rpm until it hits its rev limiter at 5800 rpm  and also when the car is cold and just started it will rev past 2500 rpm but if you try a second time, it will revert to the same issue of not wanting to rev past 2500 rpm. Yeah i know you must be thinking fuck that is weird haha.

 

It has got me stumped and many others as well, i have tried 2 different coil packs, O2 sensors on the exhaust and have cleaned the throttle body, i have also replaced the fuel rail and injectors with another set with no success. I have also swapped the ECU with another ECU but however was from the series 3 AU (i'm running a series 1 AU ecu and electrics) so the engine did not idle properly but i still took it for a test drive and it was still refusing to rev past 2500 rpm.

 

It is very frustrating  as i am not able to use 3/4's of the engine's power however on the positive side i am gaining good fuel economy with the rev restriction haha

 

Possible reason why i think  this is happening

 

1. -poor fuel pressure in the fuel rail,

 

i have replace the fuel rail and along with that with the fuel pressure reg and i doubt the bosch 044 pump would be struggling to supply good fuel pressure to a stock AU engine. Fuel filter is also brand new. So possibly the factory strainer at the end of the fuel sender pick up causing a restriction?

 

2. Something wrong with EFI setup, could a faulty knock sensor, MAF sensor, TPS, crank and cam sensor etc cause a problem like this?

 

3. Bad spark

 

As stated above i have already tried 2 different coil packs with no sucees, the spark plugs and brand new and i gaped each one to 1mm as per AU workshop information. Leads seem to be fine and the fact the engine revs past 2500 in neutral with no issues so that backs up my reasoning

 

 

 

Any help would be appreciated and this is the last resort before i get my cousin to work out the issue for me.

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hmm how can one till if the engine is in Limp mode with a manual trans? i though limp mode only occurred on engines with an auto and meant the tranny was stuck in 3rd. I've also got the J3 clip to remove limp mode all together.

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Do you have the neutral switch in the side of the gearbox hooked up? Also is it a manual or auto ecu? Is it a V8 or 6cyl tach?

 

Nope neutral switch is not hooked up, ecu is a auto one that has been converted over to manual one via the J3 chip. Tacho is actually a V8 tacho as i fitted a 6cyl one but the gauge was stuffed so i changed it to a working v8 one. However the tacho reads quite accurate and shows engine is idling at 700rpm.

 

Do the 044 boschs need a lift pump.. Are u running one?

 

Just running the 044 pump on its own, don't know if it requires one but seems to flow back plenty of fuel down the return line while idling.

 

Checked the j3 port? Sorry bro just throwing ideas.

 

I have checked it and cleaned it, also did the same from scratch with the series 3 ECU. Unless the actual  chip it's self is faulty. No need to apologize any ideas are good at this point, cheers.

 

 

 

Are you running a cat? if so check to make sure it isn't blocked or collapsed

 

 

Yep i am running one, i checked when installing it and it was fine. If the cat is blocked wouldn't it stop the engine from reving in neutral as well?

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Pull the chip and see if it fixes the problem issue? my xr6 did it when it was boosted and manual thorm is on the right parth but 
 

I gather your not running a manual ECU? if so i dont think the j3 will let you pull it out but try it anyway im sure you will have to plug the swith in like thorm said it will not work without it and the speed sensor 

this is another reason why i dont have a Xcar with a 4litre in it there prooblemish enough in a boxcar, opps did i say that out loud

But anyway pull the chip and try it, it was the issue in mine

Edit more info since the last post

The V8 tacho i dont think will like you, i think the speed sensor is somhow controled by it and it hates you for changing it it may not be a issue but if the chip will not fix it look there and hook the auto stuff up even thow its manual

So many issues come from not running the manual ecu fords are brain dead without them  

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Sounds like it could be the knock sensor retarding spark and fuel. Theses sensors are at the age where they are developing cracks and sometimes going bananas at idle. They have a piezo crystal in them that produces a voltage when knocked around, the voltage goes back to the ecu yadda yadda....

Use a multimeter to check for voltage output after visual inspection for cracks. If all good look at TPS in particular poor connection.

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Pull the chip and see if it fixes the problem issue? my xr6 did it when it was boosted and manual thorm is on the right parth but 

 

I gather your not running a manual ECU? if so i dont think the j3 will let you pull it out but try it anyway im sure you will have to plug the swith in like thorm said it will not work without it and the speed sensor 

 

this is another reason why i dont have a Xcar with a 4litre in it there prooblemish enough in a boxcar, opps did i say that out loud

 

But anyway pull the chip and try it, it was the issue in mine

 

Edit more info since the last post

 

The V8 tacho i dont think will like you, i think the speed sensor is somhow controled by it and it hates you for changing it it may not be a issue but if the chip will not fix it look there and hook the auto stuff up even thow its manual

 

So many issues come from not running the manual ecu fords are brain dead without them  

 

I haven't pulled out the chip with the engine running as wouldn't smart lock then come on and turn the engine off. Hmm interesting so your saying that because the ecu was an auto that is converted to a manual via the chip it is still depend on the speed sensor. So do think that if i just use a manual series 1 ecu with the chip just to remove the smart lock it should ok then?

 

No regrets on the conversion, still the best thing i have done to the car and the sheer smoothness and fuel consumption is sensational!

 

I know the v8 tacho won't read 100% right but whether the car cuts in and out at 2500 or 3000 doesn't really matter, the problem is still occurring.

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Is it dependent on load? Can you feather it slowly past that point or is it a sudden cut-off? If so I'm leaning towards neutral switch. Knock sensor will only come in under load. Not sure about AUs, but BAs have a rev limiter when in neutral to stop you revving it up and slamming it into gear. If that's the same with yours, sounds like could be doing things opposite to what it should. Maybe it thinks it's in neutral when in gear? Have you done anything to make it think it's not in neutral? 2500 on a V8 tach is 3333 rpm when hooked up to a 6

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.2 crank and cam angle sensor

 

I'll change them as i do have spares of each  and see if it makes a difference.

 

 

Sounds like it could be the knock sensor retarding spark and fuel. Theses sensors are at the age where they are developing cracks and sometimes going bananas at idle. They have a piezo crystal in them that produces a voltage when knocked around, the voltage goes back to the ecu yadda yadda....

Use a multimeter to check for voltage output after visual inspection for cracks. If all good look at TPS in particular poor connection.

 

Interesting you say that as the Knock sensor is from a sereis 2 AU and wouldnt that cause a problem with a sereis 1 ecu ? I'll just change it and even the TPS sensor see if that makes a difference.

 

 

 

Is it dependent on load? Can you feather it slowly past that point or is it a sudden cut-off? If so I'm leaning towards neutral switch. Knock sensor will only come in under load. Not sure about AUs, but BAs have a rev limiter when in neutral to stop you revving it up and slamming it into gear. If that's the same with yours, sounds like could be doing things opposite to what it should. Maybe it thinks it's in neutral when in drive? Is your shift quadrant in sync with the linkage?

 

I would say it is mainly dependent on load but it tends to vary as at one point it was still cutting out even revving in neutral. If you feather it slowly it will still refuse to go past that point only the cut off is less violent. I'm not sure how the neutral switch can cause this issue as it is just a safety feature that stops one starting the car in gear, if i was to wire it up it would be through the XC loom. Hmm seems like the Auto ecu is reason for these troubles.

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had a faulty tacho cause a similar issue

 

did you remove the resistor wire to the coil from the oil points system?

 

Problem occurs with the tacho connected or disconnected, resistor wire was deleted but keep in mine however the car is on coil packs so tacho signal comes from the ecu also the old coil wire is now simply an ING source.

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i would just unplug your ECU and put another one in. could be a fault with the ECU or the J3. also try putting the car on stands get in it put it in first and slowly get it to 2500rpm. get someone in the engine bay listening for anything. when its in the air and not under load it might uncover a issue. 

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i have heard of the AU having faults with crank angle sensor not reading past a certain rpm and then cutting fuel. but yours is working find in N so being a manual there should be no difference in the ECU map between N and 1st so yeah. good luck

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I'm not sure how the neutral switch can cause this issue as it is just a safety feature that stops one starting the car in gear, if i was to wire it up it would be through the XC loom. Hmm seems like the Auto ecu is reason for these troubles.

 

When doing a manual conversion in my EF, I had to bridge that neutral switch connector so it would start and also put a particular resistor into one of the wires so the computer thought it was plugged into the gear position sensor (which is a variable resistor inside the auto box) and in "drive". Otherwise it would think it was in neutral. Never quite fixed the high idle problem until I fucked with the ISC valve itelf.

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I haven't pulled out the chip with the engine running as wouldn't smart lock then come on and turn the engine off. Hmm interesting so your saying that because the ecu was an auto that is converted to a manual via the chip it is still depend on the speed sensor. So do think that if i just use a manual series 1 ecu with the chip just to remove the smart lock it should ok then?

 

No regrets on the conversion, still the best thing i have done to the car and the sheer smoothness and fuel consumption is sensational!

 

I know the v8 tacho won't read 100% right but whether the car cuts in and out at 2500 or 3000 doesn't really matter, the problem is still occurring.you dont

you dont have to pull it with it running and yes the smart lock may be a issue for you as i did not think of that my xr does not have that issue as its factory fitment to that car 

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Well hi guys just an update, I wired up the wires for the neutral safety switch in the au loom by bridging them over and no luck on that. I took it for a drive around the block and still the same issue, what was even more strange is that when i parked the car back inside it refused to go past 2500 rpm in neutral as well. While the car was running i unplugged the coolant sensor to see if would make any difference, and all it did was make the engine idle higher but when reved it still refused to go past 2500. I then switch off the car, plugged the sensor back engine and started the car. This time round the car was able to now rev past 2500 and hit the limiter, I did 3 pulls and the car was able to all 3 times rev past the 2500 and hit the limiter three times in neutral. Not sure what i should do next, i'm thinking of swapping out the crank and cam sensors?

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